The present invention relates generally to a protective film that coats a metal substrate. More particularly, the present invention relates to a thin adhesion layer for a surface of a magnetic read/write head that exhibits sufficient adhesive properties and improved corrosion resistance.
Disc drive storage systems are used for storage of digital information that can be recorded on concentric tracks of a magnetic disc medium. Several discs are rotatably mounted on a spindle, and the information, which can be stored in the form of magnetic transitions within the discs using a write transducer, is accessed using a read transducer. The read and/or write transducer is carried by a slider that is located on an actuator arm that moves radially over the surface of the disc. The slider and transducer can be collectively referred to as a magnetic head.
The discs are rotated at high speeds during operation. As the discs are spun, the slider and the read and/or write transducer glide above the surface of the disc on a small cushion of air. Upon reaching a predetermined high rotational speed, the head floats in air at a predetermined distance from the surface of the disc where it is maintained during reading and recording operations. In order to maximize the high areal recording density, the flying height (i.e. the distance by which the head floats above the surface of the disc) must be minimized.
It is well known in the art to coat the air bearing surfaces of the head and the disc with a diamond like carbon (DLC) protective overcoat and/or a lubricant layer. The function of the DLC overcoat is to protect underlying metals and alloys from wear and corrosion during the manufacturing process, and throughout the lifetime of the disc drive system. As applied to the head, the DLC overcoat includes a DLC layer and an adhesion layer. DLC overcoat thickness for the head can range from about 20 to 30 Angstroms while typical values of DLC overcoats for magnetic media are in excess of 30 Angstroms. The DLC overcoat thicknesses, along with the lubricant thickness, are the biggest contributors of head media separation (HMS) distance. The HMS distance is measured from the magnetic surface of the head to the magnetic surface of the media. The HMS distance in turn affects the data reading and writing efficiency of the transducer.
The adhesion layer of the DLC overcoat is used to attach the DLC layer to the surface of the head. It is well known in the art to use silicon for the adhesion layer. However, silicon provides limited corrosion protection, and moreover, if a silicon adhesion layer is made thinner, the DLC overcoat becomes vulnerable to reliability failure due to weakened adhesion, reduced corrosion resistance, or both.
There is a need to decrease the HMS distance, and increase recording areal density, through use of a thinner DLC overcoat that still exhibits sufficient adhesion properties and improved corrosion resistance.